The present invention relates to a method of and a system for evaluating a defective ratio in which easiness of occurrence of defects in products is evaluated before the products are manufactured.
As a known example to evaluate easiness of defective occurrence in products before manufacturing thereof, there has been reported, for example, a technology in which a defective ratio of the completed article, i.e., the entire product is estimated in accordance with the number of assembly work steps and the number of assembly parts using an average process capacity value and an average part defective ratio.
Examples of the conventional technology are described in xe2x80x9cClose-up: The 1998 International Forum on DFMAxe2x80x9d, Nikkei Mechanical, No. 526, July 1998, pp. 30-33; xe2x80x9cSix Sigma and DFMAxe2x80x9d, Nikkei Mechanical Seminar, Jul. 15, 1998, pp. 8-10 and 27-28; and JP-A-10-334151.
However, in either conventional examples, since the product defective ratio is evaluated by paying attention to assembly of parts constituting each product, a defective ratio of the product cannot be fully evaluated depending on cases when a cause of defects is included in design structure itself. For example, in evaluation of work such as soldering or welding, a defective event is apt to appear due to design structure. Therefore, for a product for which a plurality of types of defective events exist due to such design structure, the conventional defective ratio evaluation achieved by mainly paying attention to the assembly work cannot easily check all defective events and it is difficult to reflect the defective events in the evaluation.
It is therefore an object of the present invention, which has been devised to solve the conventional problem above, to provide an evaluation method and an evaluation system suitable to evaluate products for which a plurality of types of defective events exist.
To achieve the object above in accordance with the present invention, there is provided a method including a step of classifying defective information describing features of product design structure causing occurrence of product defects and storing classified information, a step of comparing design information of products to be evaluated with the defective information and calculating types and the number of defective information items included in the design information, and a step of calculating, by use of the types and the number of defective information items thus calculated, a degree in which the product becomes defective.
In addition, there is provided a system including a storage unit for classifying defective information describing features of a product design structure causing occurrence of product defects and for storing information classified, an input unit for inputting design information of products to be evaluated, and a calculating unit for comparing the design information inputted by the input unit with the defective information stored in the storage unit, for calculating types and the number of defective information items included in the design information, and for calculating, by use of the types and the number of defective information items thus calculated, a degree in which the product becomes defective.
By evaluating mainly the defective events above, it is possible to provide sufficient evaluation for products for which a plurality of types of defective events exist. Since the defective events are particularly evaluated in association with the product structure, the evaluation results directly influence quality of the product structure and hence are suitable as measures to determine necessity of design modification or correction. Additionally, the product structure related to defective events is stipulated by design information between parts and between structural conditions such as mount conditions. Therefore, it is possible to increase a chance or probability of occurrence of defective events regarding the product structure stipulated, which increases reliability of the evaluation itself.
In accordance with the present invention, there is provided an evaluation method and an evaluation system suitable to evaluate products for which a plurality of types of defective events exist.